Zinc protoporphyrin (ZPP) measurement is a required test under the Occupational Safety and Health Administration's lead standard. However, there is no mention of the influence of hemoglobinopathy on the ZPP test value. We undertook a retrospective laboratory review of 382 employees at the Argonne National Laboratory who had been subjects in a lead surveillance program since 1982. A total of 321 samples were analyzed, after female subjects and samples with abnormally high bilirubin levels were excluded. A group with low mean red blood cell volume (MCV; less than 80.0 fL) was compared with a group with normal MCV (greater or equal to 80.0 fL). A statistically significant difference was noted in ZPP (P < 0.007) and total bilirubin (P< 0.0003) values of two groups. There was no statistically significant difference noted in age, lead levels, or iron levels between the two groups. Abnormally high ZPP levels may occur in individuals with hemoglobinopathies. Only a minor part of this elevation could be explained by the higher bilirubin levels.